Based on several preliminary monkey studies conducted during the last reporting period, a working experimental protocol was synthesized. Experiments began in late October, 1989 and have continued at the rate of about one every six weeks. Each experiment seeks to detect and locate changes in regional cerebral blood volume and blood flow when the (anesthesized) animal is exposed (with eyes open) to several different kinds of visual stimuli. Imaging is performed with scintillation cameras operated in the planar mode and with flow and volume tracers labelled with Tc-99m, a single photon emitter. Stimulus induced flow and volume variations have been observed in the primary visual cortex as expected. In addition, several other effects have been observed for which there is no ready explanation. Collectively, these early results suggest that this animal model/experimental design is capable of shedding light on the functional organization of the primate brain. Two small field-of-view scintillation cameras are under development to support this work. During this period, all mechanical components (packaging of detectors, imaging table, supports, etc.) were fabricated for the prototype system and a large body of camera performance data was generated for each device. These data indicated the need for spatially- varying gain and linearity corrections and methods for making these corrections are now being investigated. These same performance data indicate that the intrinsic spatial resolution of the system with a 4 mm thick NaI crystal as the detector is less than 2 mm.